Updated on January 22, 2025.
In the U.S., nearly one-third of adults are overweight, and more than 42 percent are obese, according to the National Institutes of Health. Obesity puts people at higher risk for a long list of chronic health issues including heart disease, high blood pressure, stroke, type 2 diabetes, osteoarthritis, sleep apnea, and certain types of cancer.
But there is no simple solution for the obesity epidemic, which has been brewing for decades. Diet and exercise are just two factors involved in a complex public health issue. For example, social determinants of health—where people live and work as well as their access to healthy foods, healthcare, recreational spaces, education, and support systems—play a role. Lifestyle factors, like sleep loss, time spent sitting, mental health conditions, mobility issues, and genetics also influence people’s ability to maintain a healthy weight.
Learn more about the factors that affect weight and metabolism--and what steps you can take to help protect your long-term health.
Understanding your metabolism
Metabolism is the process by which the body burns calories from food to create energy for everyday living. Everyone is different. Some people have a “faster” metabolism than others, which means they burn more calories at rest and during activities than someone with a “slower” metabolism. The energy you need to keep your bodily functions running smoothly is called your basal metabolic rate, or BMR. This is primarily determined by your genetics. This may be one reason why some people can eat more than others without gaining weight. But your activity level and exercise can also affect your metabolism.
You may have heard that metabolism slows with age. And while that may be true, recent research shows this doesn’t actually happen until much later in life than previously thought, or until people are in their 60s or older.
Research also shows that even small changes to daily caloric intake may lead to more significant changes over time. So, taking in just a few extra calories each day (which may seem insignificant) can contribute to weight gain after one year. But cutting the same number of calories for the same duration of time can be an effective weight loss strategy.
Muscle mass matters
Muscle burns more calories than fat—even at rest. So, the more muscle you have, the high your resting metabolic rate may be. Doing muscle-building activities in addition to cardiorespiratory activities (such as running, biking, or walking) can also support your bone health, improve your mobility, and generally boost your confidence as you gain strength.
But keep in mind, muscle tissue is denser than fat. So, while one pound of muscle is not heavier than one pound of fat, it takes up less space. As a result, weight gain may be a sign of muscle growth, which is a good thing. Muscles can also retain water, which may affect the number you see on a scale.
This is why it’s important to remember that scales are helpful tools, but they may be deceiving. Stepping on a scale once a week or twice a month can help you track your weight and notice subtle changes over time. But weight can fluctuate daily for a variety of reasons, including water intake or retention, hormones, and other factors. And for some people, daily weigh-ins can do more harm than good, eroding their self-confidence and well-being. Be sure to keep the number on the scale in perspective.
Why experts are rethinking BMI
Body mass index (BMI), which is a calculation used to determine if someone is a healthy weight for their height, is a flawed measure.
For years, BMI has been used to estimate people’s percentage of body fat and determine if they were overweight or obese. It’s calculated by dividing someone’s weight in kilograms by the square of their height in meters. If the number is high, it suggests high body fatness. A low BMI indicates low body fatness. The categories associated with BMI are:
- Below 18.5: Underweight
- 18.5-24.9: Healthy weight
- 25.0-29.9: Overweight
- 30.0 and above: Obese
These ranges are slightly different for Asian and Asian American adults. But based on BMI, some people with a high BMI, such as athletes, may have normal or even low body fat mass. Meanwhile, some with low BMI scores may have excess body fat. It’s important to recognize that BMI is not the only measure of a person’s overall health. In fact, in January 2025, 58 scientists published a report in The Lancet Diabetes & Endocrinology, recommending that factors other than BMI are also considered when assessing obesity, such as waist circumference and evidence of health problems tied to excess weight, such as heart disease, high blood pressure, liver or kidney disease, or chronic severe knee or hip pain.
BMI alone does not gauge a person’s actual body composition, health, or fitness. It may be a starting point that your HCP uses to make a full assessment of your health. Other tools that can help measure your overall fitness include skinfold thickness and evaluations of diet, physical activity, and family history.
Know your caloric needs
Most adults should get between 1,300 and 3,000 calories per day. What is right for you depends on a range of variables, including your sex, height, weight, age, hormone levels, activity level, muscle mass, and any medications you may be taking.
You can work with your HCP to determine what your daily calorie needs are and what is a healthy weight for you. From there, it’s about finding a balance. If you consume fewer calories than you need, you may lose weight over time. If you regularly consume additional calories, you may gain weight. And if you stick to your calorie goal, you’ll likely be setting yourself up for effective weight management.
Reviewing the foods you eat regularly can help you reach your daily calorie goals or maintain a healthy weight. Key components of a healthy diet include:
- A wide variety of fruits and vegetables. Try to “eat the rainbow,” or consume produce of many different colors, such as red, green, or yellow peppers, blueberries, raspberries, leafy greens, avocado, and more.
- Grains, including lentils, quinoa, and brown rice. At least half of your intake should come from 100-percent whole grains—not refined grains like white rice.
- Fat-free or low-fat dairy products, like yogurt
- Lean proteins, such as poultry, fish, eggs, and plant-based sources such as beans, nuts, and tofu
- A small amount of olive oil and other healthy monounsaturated facts that come from seafood, vegetables, or nuts
Meanwhile, a healthy eating plan should limit:
- Added sugars, which are often found in processed or packaged foods, condiments, sauces, dressings, and beverages
- Saturated fat, which comes mostly from animal products such as red meat and butter, but also from some plant-based sources like palm and coconut oils. Limit saturated fat to less than 10 percent of the total calories you eat each day.
- Sodium, which is often found in processed or packaged foods. Ideally, you should get less than 2,300 milligrams a day.
- Alcohol, which should top out at no more than two drinks a day for men and one drink a day for women. Less is better, and if you don’t already drink alcoholic beverages, don’t start.
Other smart strategies for a healthy eating plan, include:
- Stick to regular meal and snack times to avoid grazing during the day or overeating due to skipped meals.
- Avoid eating in front of the TV or other screens. Try to be mindful of your food and chew slowly to allow your brain time to signal when you’re full.
- Practice smart portion control. It may help to avoid putting large servings bowls on the table. Instead, portion out your meal before sitting down. This can help you stick to your calorie goals.
Move more throughout the day
Aim to exercise every day, or just move your body more. For health benefits, including effective weight management, adults should get between 150 minutes (2 hours and 30 minutes) and 300 minutes (5 hours) of moderate-intensity exercise each week. Think brisk walking or working in the yard. Alternatively, you can aim for75 minutes (1 hour and 15 minutes) to 150 minutes of vigorous-intensity aerobic activity each week. That might be running, swimming laps, or taking an interval training class. You can also mix and match your workouts, doing moderate exercise on some days and more vigorous activities on others.
All adults are also advised to include some form of muscle-strengthening exercise twice a week. These moves should hit your major muscle groups. Think lifting weights, using resistance bands, or doing body weight or weight-free moves like pushups, squats, or water aerobics.
If you are able, doing more than the minimum recommended amount of exercise may be even better. The more active you are, the greater the health benefits. Just be sure to check with your HCP before you start or change an exercise program.
Poor sleep may affect your weight
If you don’t rest enough on a regular basis, you may have a harder time maintaining or losing weight. You might assume this connection is simply because people who stay up late or don’t have a well-established sleep-wake routine are just too tired to be active or to work out. But the sleep-metabolism connection is more complex than that.
Research suggests that sleep loss affects hormone levels tied to hunger, satiety, stress, and even insulin sensitivity. The more sleep deprived you are, the more profound these effects will be. Routinely getting at least seven hours of quality sleep each night can help support your health goals.
Is a weight-loss drug right for you?
Studies show drugs called GLP-1s are highly effective in helping people lose weight. In fact, one March 2021 study published in the New England Journal of Medicine found that patients on semaglutide—one of seven GLP-1s—lost an average of 15 percent of their body mass.
How do these drugs work? Eating causes the gut to release a hormone called glucagon-like peptide 1 (GLP1), which triggers the release of insulin to help regulate blood sugar levels. But GLP1 also slows digestion, helps promote a feeling of fullness, and helps control appetite, making GLP-1s effective weight loss tools—when used in addition to lifestyle adjustments, such as regular exercise, adequate sleep, changes in behavior or thinking patterns and following a healthy eating plan.
In addition to regulating blood sugar and assisting weight loss, GLP-1s may also help:
- Lower blood pressure
- Improve cholesterol and fatty liver disease
- Reducing the risk of heart and kidney disease
- Delaying the progression of diabetes-related nerve damage
GLP-1s have been studied and are designed for weight loss in people with a BMI of at least 27 and at least one weight-related condition. The safety of using the drugs for more cosmetic weight loss—say shedding 10 to 15 pounds—isn’t clear. Talk to your HCP about whether one of these medications is safe or appropriate for you.
Start small for big benefits
When it comes to setting goals, including health goals, it usually helps to start by making small changes in your routine. You can even stack these new healthy behaviors onto existing habits. For example, if you’re trying to drink more water and hydrate better, have a glass each morning after you brush your teeth. This can help you transform new behaviors that you need to think about each day into habits that are second nature. Some small healthy changes you could make to your daily routine, include:
- Be more active in everyday tasks. Park at the back of the supermarket parking lot so you take more steps. March in place while you watch TV. Walk around while talking on the telephone. These moves add valuable minutes of physical activity to your day.
- Try new activities to help you increase your activity level. Are you getting bored of walking around your block? Seek out new routes or explore hiking trails on the weekend.
- Exercise with a friend or a group. Social interaction combined with physical activity is a win-win for your physical and mental well-being.
- Replace sugar-sweetened drinks with zero- or low-calorie beverages. Try spritzing some fresh lemon or lime into seltzer water instead of drinking sugary soda or juice.
